BackgroundEndothelial progenitor cells (EPCs) play a fundamental role in post-natal vascular repair. Currently EPCs are defined as either early and late EPCs based on their biological properties and their time of appearance during in vitro culture. EPCs are rare and therefore optimizing isolation and culture is required before they can be applied as part of clinical therapies.ResultsWe compared the gene profiles of early/late EPCs to their ancestors CD133+ or CD34+ stem cells and to matured endothelial cells pinpointing novel biomarkers and stemness genes. Late EPCs were enriched with proliferation and angiogenesis genes, participating in endothelial tubulogenesis and hence neovascularization. Early EPCs expressed abundant inflammatory cytokines and paracrine angiogenic factors, thereby promoting angiogenesis in a paracrine manner. Transcription factors involved in EPC stemness were pinpointed in early EPCs (MAF/MAFB) and in late EPCs (GATA6/IRF6).ConclusionsThe detailed mRNA expression profiles and functional module analysis for different EPCs will help the development of novel therapeutic modalities targeting cardiovascular disease, tumor angiogenesis and various ischemia-related diseases.

Dysfunction and reduction of circulating endothelial progenitor cell (EPC) is correlated with the onset of cardiovascular disorders including coronary artery disease (CAD). VEGF is a known mitogen for EPC to migrate out of bone marrow to possess angiogenic activities, and the plasma levels of VEGF are inversely correlated to the progression of CAD. Circulating microRNAs (miRNAs) in patient body fluids have recently been considered to hold the potential of being novel disease biomarkers and drug targets. However, how miRNAs and VEGF cooperate to regulate CAD progression is still unclear. Through the small RNA sequencing (smRNA-seq), we deciphered the miRNome patterns of EPCs with different angiogenic activities, hypothesizing that miRNAs targeting VEGF must be more abundant in EPCs with lower angiogenic activities. Candidates of anti-VEGF miRNAs, including miR-361-5p and miR-484, were enriched in not only diseased EPCs but also the plasma of CAD patients. However, we found out only miR-361-5p, but not miR-484, was able to suppress VEGF expression and EPC activities. Reporter assays confirmed the direct binding and repression of miR-361-5p to the 3′-UTR of VEGF mRNA. Knock down of miR-361-5p not only restored VEGF levels and angiogenic activities of diseased EPCs in vitro, but further promoted blood flow recovery in ischemic limbs of mice. Collectively, we discovered a miR-361-5p/VEGF-dependent regulation that could help to develop new therapeutic modalities not only for ischemia-related diseases but also for tumor angiogenesis.

Objective-Defects in angiogenesis/vasculogenesis or vessel repair are major complications of coronary artery disease (CAD). Endothelial progenitor cells (EPCs) play a fundamental role in postnatal vascular repair and CAD. The role of microRNAs in CAD pathogenesis and their potential as biomarkers remain to be elucidated. Approach and Results-MicroRNA-31 (miR-31) level in both the plasma and EPCs of patients with CAD is found lower.miR-31 regulates EPC activities by targeting FAT atypical cadherin 4 and thromboxane A2 receptor, which show increased expression in CAD EPCs. Overexpressing miR-31 in CAD EPCs rescued their angiogenic and vasculogenic abilities both in vitro and in vivo. When exploring approaches to restore endogenous miR-31, we found that far-infrared treatment enhanced the expression of not only miR-31, but also miR-720 in CAD EPCs. miR-720, which was also decreased in EPCs and the plasma of patients with CAD, stimulated EPC activity by targeting vasohibin 1. The miR720-vasohibin 1 pair was shown to be downstream of FAT atypical cadherin 4, but not of thromboxane A2 receptor. FAT atypical cadherin 4 inhibited miR-720 expression via repression of the planar cell polarity signaling gene four-jointed box 1 (FJX1), which was required for miR-720 expression through a hypoxia-inducible factor 1, α subunit-dependent mechanism. Restoring miR-720 level strengthened activity of CAD EPCs. The miR-31-miR-720 pathway is shown critical to EPC activation and that downregulation of this pathway contributes to CAD pathogenesis. Circulating levels of miR-31, miR-720, and vasohibin 1 have the potential to allow early diagnosis of CAD and to act as prognosis biomarkers for CAD and other EPC-related diseases. In addition to the number of circulating EPCs present, the regulation of postnatal angiogenesis/vasculogenesis also depends on the activity of mobilized EPCs. 8 In addition to the effects of protein-coding genes, the expression of various different microRNAs (miRNAs, miRs) also plays a critical role in the clinical course of CAD. miRNAs are a class of endogenous, small, noncoding, single-stranded RNAs of ≈22 nucleotides in length. The mature miRNAs negatively regulate gene expression by targeting specific mRNAs for cleavage or translational repression. Detecting the levels of tissue miRNAs, as well as the levels of circulating miRNAs in body fluids, is considered to be a potential approach to identifying new disease biomarkers and novel drug targets. Conclusions-Manipulating9-11 Many proangiogenic and antiangiogenic miRNAs have been pinpointed. Examples such as miR-221 and miR-222, which are transcribed from the same miR-221/222 cluster, have been shown to be able to modulate the angiogenic properties of human umbilical vein endothelial cells by targeting c-Kit and endothelial NO synthase.12,13 miR-221/222 levels in EPCs are significantly higher in patients with CAD.14,15 miR-10a* and miR-21 are also known to modulate EPC senescence via the suppression of high-mobility group A2.16 miR-10b and miR-196b, on the cont...